Hormonal Regulation of the Reproductive

System

1. Primary sex characteristics (gonads and sperm) are produced while the fetus is still in utero (testes descend into scrotum at third month of development).

2. Secondary sex characteristics (body/facial hair, growth of larynx, muscle strengthening) occur at puberty due to hormonal changes.

Hormonal Control

Hormonal Control At Puberty

1. Hypothalamus• Releases gonadotropic releasing hormone (GnRH)• First released at puberty. • GnRH causes the Pituitary to release:

2. Pituitary• Follicle Stimulating Hormone (FSH) – Stimulates sperm

production in seminiferous tubules.• Lutenizing Hormone (LH) – promotes testosterone production

(which then promotes sperm production).

Hormonal Control At Puberty

Interstitial Cells• Interstitial cells in testes produce testosterone

when stimulated by LH. • Testosterone stimulates spermatogenesis and

development of secondary sex characteristics.

Testosterone & Sperm Production are Controlled by Negative Feedback

• Testosterone deactivates the hypothalamus, inhibiting the production of LH by the pituitary.

• Sertoli cells inhibit the hypothalamus from secreting GnRH and the pituitary from secreting FSH.

Interesting Facts Castratis – Male sopranos popular in 17 and 18

Centuries

Prostate cancer is one of the most common cancers in males. (In Canada, 81 Canadian men die from prostate cancer every week). It is detected via blood tests for PSA or through the digital rectal exam. Men over the age of 50 should be examined yearly.

Menstrual Cycle

Puberty in Females Begins when GnRH

levels increase

Recognized with first episode of menstrual bleeding

Menstrual Cycle Facts About 28 days long Phases

◦ Flow phase◦ Follicular phase◦ Ovulation event◦ Leuteal phase

Amenorrhea: Absence of a menstrual cycle Menopause: Cessation of menstrual cycles

Ovarian cells involved primary oocyte

◦ becomes ovum for fertilization

granulose or follicle cells◦ provide nourishment

ovaries undergo continual decline after onset of puberty

500+ follicles start to develop during every cycle, but only a single follicle becomes dominant & reaches maturity.

Oogenesis Overview

Maturation of Follicle and Oocyte

Controlled by Hormones Hypothalamus

◦ gonadotropin-releasing hormone (GnRH) targets pituitary.

Pituitary◦ FSH starts egg

maturation.◦ LH triggers ovulation,

and formation of corpus luteum.

Ovary◦Granulose cells

Estrogen promotes thickening of endometrium.

◦Corpus luteum estrogen and

progesterone maintains lining.

Cycle SummaryFlow Follicular Ovulation (event) Luteal

shedding of endometrial lining

Day 1 – 5

NO HORMONES

development of follicles within ovaryestrogen triggers thickening of endometrium

Day 6 – 13

High FSH, then estrogen, ends with LH spike.

Oocyte (egg) bursts from ovaryfollicle cells become corpus luteum

Day 14

Highest LH Point

corpus luteum secretes estrogen and progesteronemaintains lining, inhibits ovulation

Day 15 – 28

High progesterone and estrogen

Cycle and Cells

Surgical Birth Control

Tubal Ligation

Procedure fallopian tubes are

cut, burned, or blocked with rings, bands or clips.

now under local anaesthesia.